2002 JEEP GRAND CHEROKEE AC FAN

INSPECTION
The radiator cooling fins should be checked for
damage or deterioration. Inspect cooling fins to make
sure they are not bent or crushed, these areas result
in reduced heat exchange causing the cooling system
to operate at higher temperatures. Inspect the plastic
end tanks for cracks, damage or leaks.
Inspect the radiator neck for damage or distortion.
INSTALLATION
CAUTION: Before installing the radiator or A/C con-
denser, be sure the radiator-to-body and radiator-to-
A/C condenser rubber air seals (Fig. 39) are
properly fastened to their original positions. These
are used at the top, bottom and sides of the radia-
tor and A/C condenser. To prevent overheating,
these seals must be installed to their original posi-
tions.
(1) Equipped with air conditioning: Gently lower
the radiator into the vehicle. Guide the two radiator
alignment dowels through the holes in the rubber air
seals first and then through the A/C support brackets
(Fig. 40). Continue to guide the alignment dowels
into the rubber grommets located in lower radiator
crossmember. The holes in the L-shaped brackets
(located on bottom of A/C condenser) must be posi-
tioned between bottom of rubber air seals and top of
rubber grommets.
(2) Connect the radiator upper and lower hoses
and hose clamps to radiator (Fig. 41).
CAUTION: The tangs on the hose clamps must be
positioned straight down.
(3) Install coolant reserve/overflow tank hose at
radiator (Fig. 41).
(4) Connect both transmission cooler lines at the
radiator (Fig. 41).
(5) Install both radiator mounting bolts (Fig. 41).
(6) Install air inlet duct at grill.
(7) Attach electric fan harness to shroud, then con-
nect harness to connector (Fig. 41).
(8) Install the grill (Refer to 23 - BODY/EXTERI-
OR/GRILLE - INSTALLATION).
(9) Install the fan/viscous fan drive assembly to
the water pump.
(10) Rotate the fan blades (by hand) and check for
interference at fan shroud.
(11) Be sure of at least 25 mm (1.0 inch) between
tips of fan blades and fan shroud.
(12) Fill cooling system (Refer to 7 - COOLING -
STANDARD PROCEDURE).
(13) Connect battery cable at battery.
(14) Start and warm engine. Check for leaks.
RADIATOR FAN MOTOR
DIAGNOSIS AND TESTINGÐELECTRIC
COOLING FAN
The powertrain control module (PCM) will enter a
diagnostic trouble code (DTC) in memory if it detects
a problem in the auxiliary cooling fan relay or circuit.
(Refer to 25 - EMISSIONS CONTROL - DESCRIP-
TION).
If the electric cooling fan is inoperative, check the
15A fuse in the junction block and the 40A fuse in
the Power Distribution Center (PDC) with a 12 volt
test lamp or DVOM. Refer to the inside of the PDC
cover for the exact location of the fuse. If fuses are
okay, refer to ELECTRICAL for cooling fan and relay
circuit schematic.
WATER PUMP - 4.7L
DESCRIPTION
DESCRIPTIONÐWATER PUMP
A centrifugal water pump circulates coolant
through the water jackets, passages, intake manifold,
radiator core, cooling system hoses and heater core.
The pump is driven from the engine crankshaft by a
single serpentine drive belt.
The water pump impeller is pressed onto the rear
of a shaft that rotates in bearings pressed into the
housing. The housing has two small holes to allow
seepage to escape. The water pump seals are lubri-
cated by the antifreeze in the coolant mixture. No
additional lubrication is necessary.
Both heater hoses are connected to fittings on the
timing chain front cover. The water pump is also
mounted directly to the timing chain cover and is
equipped with a non serviceable integral pulley (Fig.
42).
DESCRIPTIONÐWATER PUMP BYPASS
The 4.7L engine uses an internal water/coolant
bypass system. The design uses galleries in the tim-
ing chain cover to circulate coolant during engine
warm-up preventing the coolant from flowing
through the radiator. The thermostat uses a stub
shaft located at the rear of the thermostat (Fig. 43)
to control flow through the bypass gallery.
OPERATION
OPERATIONÐWATER PUMP
A centrifugal water pump circulates coolant
through the water jackets, passages, intake manifold,
WJENGINE 7 - 47
RADIATOR - 4.0L (Continued)

CAUTION: When installing the serpentine accessory
drive belt, belt must be routed correctly. If not,
engine may overheat due to water pump rotating in
wrong direction.
(6) Refill cooling system (Refer to 7 - COOLING -
STANDARD PROCEDURE).
(7) Connect negative battery cable.
(8) Start and warm the engine. Check for leaks.
WATER PUMP - 4.0L
DESCRIPTION
CAUTION: All 4.0L 6-cylinder engines are equipped
with a reverse (counterclockwise) rotating water
pump and thermal viscous fan drive assembly.
REVERSE is stamped or imprinted on the cover of
the viscous fan drive and inner side of the fan. The
letter R is stamped into the back of the water pump
impeller. Engines from previous model years,
depending upon application, may have been
equipped with a forward (clockwise) rotating water
pump. Installation of the wrong water pump or vis-
cous fan drive will cause engine over heating.
A centrifugal water pump circulates coolant
through the water jackets, passages, intake manifold,
radiator core, cooling system hoses and heater core.
The pump is driven from the engine crankshaft by a
single serpentine drive belt.
The water pump impeller is pressed onto the rear
of a shaft that rotates in bearings pressed into the
housing. The housing has two small holes to allow
seepage to escape. The water pump seals are lubri-
cated by the antifreeze in the coolant mixture. No
additional lubrication is necessary (Fig. 45).
DIAGNOSIS AND TESTINGÐWATER PUMP
LOOSE IMPELLER - 4.0L and 4.7L
NOTE: Due to the design of the 4.0L and 4.7L
engine water pumps, testing the pump for a loose
impeller must be done by verifying coolant flow in
the radiator. To accomplish this refer to the follow-
ing procedure.
DO NOT WASTE reusable coolant. If solution is
clean, drain coolant into a clean container for reuse.
(1) Drain coolant until the first row of cores is vis-
ible in the radiator (Refer to 7 - COOLING - STAN-
DARD PROCEDURE) 4.7L Engine or (Refer to 7 -
COOLING - STANDARD PROCEDURE) 4.0L
Engine.(2) Leaving the radiator cap off, start the engine.
Run engine until thermostat opens.
(3) While looking into the radiator through the
radiator fill neck, raise engine rpm to 2000 RPM.
Observe the flow of coolant from the first row of
cores.
(4) If there is no flow or very little flow visable,
replace the water pump.
INSPECTING FOR INLET RESTRICTIONS
Inadequate heater performance may be caused by
a metal casting restriction in the heater hose inlet.
DO NOT WASTE reusable coolant. If solution is
clean, drain the coolant into a clean container for
reuse.
WARNING: DO NOT LOOSEN THE RADIATOR
DRAINCOCK WITH THE SYSTEM HOT AND UNDER
PRESSURE. SERIOUS BURNS FROM THE COOL-
ANT CAN OCCUR.
(1) Drain sufficient coolant from the radiator to
decrease the level below the heater hose inlet. On
4.7L engines this requires complete draining.
(2) Remove the heater hose.
(3) Inspect the inlet for metal casting flash or
other restrictions.
Fig. 45 Water Pump
1 - HEATER HOSE FITTING BORE
2 - WATER PUMP
3 - WATER PUMP HUB
7 - 50 ENGINEWJ
WATER PUMP - 4.7L (Continued)

NOTE: On 4.0L engines remove the pump from the
engine before removing restriction to prevent con-
tamination of the coolant with debris. . On 4.7L
engine remove the fitting from the timing chain
cover, If the restriction is in the timing chain cover,
remove the timing chain cover.
REMOVAL
CAUTION: If the water pump is replaced because of
mechanical damage, the fan blades and viscous fan
drive should also be inspected. These components
could have been damaged due to excessive vibra-
tion.
The water pump impeller is pressed on the rear of
the pump shaft and bearing assembly. The water
pump is serviced only as a complete assembly.
NOTE: The water pump can be replaced without
discharging the A/C system.
WARNING: DO NOT REMOVE THE BLOCK DRAIN
PLUG(S) OR LOOSEN RADIATOR DRAINCOCK
WITH THE SYSTEM HOT AND UNDER PRESSURE.
SERIOUS BURNS FROM COOLANT CAN OCCUR.
DO NOT WASTE reusable coolant. If the solution
is clean, drain coolant into a clean container for
reuse.
(1) Disconnect negative battery cable at battery.
(2) Drain the cooling system (Refer to 7 - COOL-
ING - STANDARD PROCEDURE).
(3) The thermal viscous fan drive is attached
(threaded) to the water pump hub shaft. Remove fan/
viscous fan drive assembly from water pump by turn-
ing mounting nut counterclockwise as viewed from
front. Threads on viscous fan drive areRIGHT
HANDDo not attempt to remove fan/viscous fan
drive assembly from vehicle at this time.
(4) If water pump is being replaced, do not unbolt
fan blade assembly from thermal viscous fan drive.
(5) Remove fan shroud-to-radiator nuts (Fig. 46).
Do not attempt to remove fan shroud at this time.
(6) Remove fan shroud and fan blade/viscous fan
drive assembly from vehicle as a complete unit.
(7) After removing fan blade/viscous fan drive
assembly,do notplace thermal viscous fan drive in
horizontal position. If stored horizontally, silicone
fluid in viscous fan drive could drain into its bearing
assembly and contaminate lubricant.
Loosen but do not remove the water pump pulley
mounting bolts.Remove accessory drive belt (Refer to 7 - COOL-
ING/ACCESSORY DRIVE/DRIVE BELTS - REMOV-
AL).
Remove the water pump pulley.
(8) Remove the idler pulley (located over the water
pump).
WARNING: CONSTANT TENSION HOSE CLAMPS
ARE USED ON MOST COOLING SYSTEM HOSES.
WHEN REMOVING OR INSTALLING, USE ONLY
TOOLS DESIGNED FOR SERVICING THIS TYPE OF
CLAMP, SUCH AS SPECIAL CLAMP TOOL (NUMBER
6094) (Fig. 47) SNAP-ON CLAMP TOOL (NUMBER
HPC-20) MAY BE USED FOR LARGER CLAMPS.
ALWAYS WEAR SAFETY GLASSES WHEN SERVIC-
ING CONSTANT TENSION CLAMPS.
CAUTION: A number or letter is stamped into the
tongue of constant tension clamps (Fig. 48). If
replacement is necessary, use only an original
equipment clamp with matching number or letter.
(9) Remove lower radiator hose from water pump.
Remove heater hose from water pump fitting.
(10) Remove the five pump mounting bolts (Fig.
49) and remove pump from vehicle. Discard old gas-
ket. Note that one of the five bolts is longer than the
other bolts.
(11) If pump is to be replaced, the heater hose fit-
ting must be removed. Note position of fitting before
removal.
Fig. 46 Fan Shroud Mounting
1 - SHROUD FASTENERS
2 - DRAIN COCK
3 - RADIATOR FAN SHROUD
4 - SHROUD FASTENERS
WJENGINE 7 - 51
WATER PUMP - 4.0L (Continued)

CLEANING
Clean the gasket mating surface. Use caution not
to damage the gasket sealing surface.
INSPECTION
Inspect the water pump assembly for cracks in the
housing, Water leaks from shaft seal, Loose or rough
turning bearing or Impeller rubbing either the pump
body or timing chain case/cover.
INSTALLATION
CAUTION: If the water pump is replaced because of
mechanical damage, the fan blades and viscous fan
drive should also be inspected. These components
could have been damaged due to excessive vibra-
tion.
(1) If pump is being replaced, install the heater
hose fitting to the pump. Use a sealant on the fitting
such as MopartThread Sealant With Teflon. Refer to
the directions on the package.
(2) Clean the gasket mating surfaces. If the origi-
nal pump is used, remove any deposits or other for-
eign material. Inspect the cylinder block and water
pump mating surfaces for erosion or damage from
cavitation.
(3) Install the gasket and water pump. The sili-
cone bead on the gasket should be facing the water
pump. Also, the gasket is installed dry. Tighten
mounting bolts to 30 N´m (22 ft. lbs.) torque. Rotate
the shaft by hand to be sure it turns freely.
(4) Connect the radiator and heater hoses to the
water pump.
(5) Position water pump pulley to water pump
hub. Tighten bolts 28 N´m (250 in. lbs.).
Install the idler pulley. Tighten the bolt 47 N´m (35
ft. lbs.).
Fig. 47 Hose Clamp Tool - Typical
1 - HOSE CLAMP TOOL 6094
2 - HOSE CLAMP
Fig. 48 Clamp - Typical
1 - TYPICAL CONSTANT TENSION HOSE CLAMP
2 - CLAMP NUMBER/LETTER LOCATION
3 - TYPICAL HOSE
Fig. 49 Water Pump Remove/Install - Typical
1 - HEATER HOSE FITTING
2 - PUMP GASKET
3 - WATER PUMP
4 - LONG BOLT
5 - BOLTS (4) SHORT
7 - 52 ENGINEWJ
WATER PUMP - 4.0L (Continued)

CAUTION: When installing the serpentine engine
accessory drive belt, the belt MUST be routed cor-
rectly. If not, the engine may overheat due to the
water pump rotating in the wrong direction. Refer to
the Belt Removal and Installtion in this group for
appropriate belt routing. You may also refer to the
Belt Routing Label in the vehicle engine compart-
ment.
Install accessory drive belt (Refer to 7 - COOLING/
ACCESSORY DRIVE/DRIVE BELTS - INSTALLA-
TION).
(6) Install fan blade and viscous fan drive onto
water pump.
(7) Fill cooling system with coolant and check for
leaks. (Refer to 7 - COOLING - STANDARD PROCE-
DURE).
(8) Connect battery cable to battery.
(9) Start and warm the engine. Check for leaks.
RADIATOR PRESSURE CAP
DESCRIPTION
All radiators are equipped with a pressure cap
(Fig. 50). This cap releases pressure at some point
within a range of 124-to-145 kPa (18-to-21 psi). The
pressure relief point (in pounds) is engraved on top of
the cap
The cooling system will operate at pressures
slightly above atmospheric pressure. This results in a
higher coolant boiling point allowing increased radi-
ator cooling capacity. The cap contains a spring-
loaded pressure relief valve. This valve opens when
system pressure reaches the release range of 124-to-
145 kPa (18-to-21 psi).
A rubber gasket seals the radiator filler neck. This is
done to maintain vacuum during coolant cool-down and
to prevent leakage when system is under pressure.
OPERATION
A vent valve in the center of the cap will remain
shut as long as the cooling system is pressurized. As
the coolant cools, it contracts and creates a vacuum
in cooling system. This causes the vacuum valve to
open and coolant in reserve/overflow tank to be
drawn through connecting hose into radiator. If the
vacuum valve is stuck shut, or overflow hose is
kinked, radiator hoses will collapse on cool-down.
DIAGNOSIS AND TESTINGÐRADIATOR
PRESSURE CAP
Remove cap from radiator. Be sure that sealing
surfaces are clean. Moisten rubber gasket with water
and install the cap on pressure tester (tool 7700 or
an equivalent) (Fig. 51).Operate the tester pump and observe the gauge
pointer at its highest point. The cap release pressure
should be 124 to 145 kPa (18 to 21 psi). The cap is
satisfactory when the pressure holds steady. It is also
good if it holds pressure within the 124 to 145 kPa
(18 to 21 psi) range for 30 seconds or more. If the
pointer drops quickly, replace the cap.
CAUTION: Radiator pressure testing tools are very
sensitive to small air leaks, which will not cause
cooling system problems. A pressure cap that does
not have a history of coolant loss should not be
replaced just because it leaks slowly when tested
with this tool. Add water to tool. Turn tool upside
down and recheck pressure cap to confirm that cap
needs replacement.CLEANING
Clean the radiator pressure cap using a mild soap
and water only.
Fig. 50 Radiator Pressure Cap - Typical
1 - FILLER NECK SEAL
2 - VACUUM VENT VALVE
3 - PRESSURE RATING
4 - PRESSURE VALVE
WJENGINE 7 - 53
WATER PUMP - 4.0L (Continued)

²Malfunction indicator lamp (Check engine lamp).
Driven through J1850 circuits.
²Overdrive indicator lamp (if equipped). Driven
through J1850 circuits.
²Oxygen sensor heater relays (if equipped).
²Radiator cooling fan relay (pulse width modu-
lated)
²Speed control source
²Speed control vacuum solenoid
²Speed control vent solenoid
²Tachometer (if equipped). Driven through J1850
circuits.
²Transmission convertor clutch circuit
²Transmission 3±4 shift solenoid
²Transmission relay
²Transmission temperature lamp (if equipped)
²Transmission variable force solenoid
OPERATION - 5 VOLT SUPPLIES
Primary 5±volt supply:
²supplies the required 5 volt power source to the
Crankshaft Position (CKP) sensor.
²supplies the required 5 volt power source to the
Camshaft Position (CMP) sensor.
²supplies a reference voltage for the Manifold
Absolute Pressure (MAP) sensor.
²supplies a reference voltage for the Throttle
Position Sensor (TPS) sensor.
Secondary 5±volt supply:
²supplies the required 5 volt power source to the
oil pressure sensor.
²supplies the required 5 volt power source for the
Vehicle Speed Sensor (VSS) (if equipped).
²supplies the 5 volt power source to the transmis-
sion pressure sensor (if equipped with an RE auto-
matic transmission).
OPERATION - IGNITION CIRCUIT SENSE
The ignition circuit sense input tells the PCM the
ignition switch has energized the ignition circuit.
Battery voltage is also supplied to the PCM
through the ignition switch when the ignition is in
the RUN or START position. This is referred to as
the9ignition sense9circuit and is used to9wake up9
the PCM.
REMOVAL
USE THE DRBIIItSCAN TOOL TO REPRO-
GRAM THE NEW POWERTRAIN CONTROL
MODULE (PCM) WITH THE VEHICLES ORIGI-
NAL IDENTIFICATION NUMBER (VIN) AND
THE VEHICLES ORIGINAL MILEAGE. IF THIS
STEP IS NOT DONE, A DIAGNOSTIC TROUBLE
CODE (DTC) MAY BE SET.
The PCM is located on the cowl panel in right/rear
side of engine compartment (Fig. 12).The PCM is located on the cowl panel in right/rear
side of engine compartment (Fig. 12).
To avoid possible voltage spike damage to PCM,
ignition key must be off, and negative battery cable
must be disconnected before unplugging PCM connec-
tors.
(1) Disconnect negative battery cable at battery.
Fig. 12 Powertrain Control Module (PCM) Location
1 - PCM
2 - COOLANT TANK
Fig. 13 Powertrain Control Module (PCM) 32±Way
Connectors
1 - 3 32±WAY CONNECTORS
2 - PCM/BRACKET ASSEMBLY
3 - BRACKET NUTS (3)
8E - 16 ELECTRONIC CONTROL MODULESWJ
POWERTRAIN CONTROL MODULE (Continued)

GENERATOR
DESCRIPTION
The generator is belt-driven by the engine using a
serpentine type drive belt. It is serviced only as a
complete assembly. If the generator fails for any rea-
son, the entire assembly must be replaced.
OPERATION
As the energized rotor begins to rotate within the
generator, the spinning magnetic field induces a cur-
rent into the windings of the stator coil. Once the
generator begins producing sufficient current, it also
provides the current needed to energize the rotor.
The Y type stator winding connections deliver the
induced AC current to 3 positive and 3 negative
diodes for rectification. From the diodes, rectified DC
current is delivered to the vehicle electrical system
through the generator battery terminal.
Although the generators appear the same exter-
nally, different generators with different output rat-
ings are used on this vehicle. Be certain that the
replacement generator has the same output rating
and part number as the original unit. Refer to Gen-
erator Ratings in the Specifications section at the
back of this group for amperage ratings and part
numbers.
Noise emitting from the generator may be caused
by: worn, loose or defective bearings; a loose or defec-
tive drive pulley; incorrect, worn, damaged or misad-
justed fan drive belt; loose mounting bolts; a
misaligned drive pulley or a defective stator or diode.
REMOVAL
WARNING: DISCONNECT NEGATIVE CABLE FROM
BATTERY BEFORE REMOVING BATTERY OUTPUT
WIRE (B+ WIRE) FROM GENERATOR. FAILURE TO
DO SO CAN RESULT IN INJURY OR DAMAGE TO
ELECTRICAL SYSTEM.
(1) Disconnect negative battery cable at battery.
(2) Remove generator drive belt. Refer to Cooling
System for procedure.
(3) Unsnap cable protector cover from B+ mount-
ing stud (Fig. 2) .
(4) Disconnect (unsnap) 2±wire field connector at
rear of generator (Fig. 2) .
(5) Remove generator mounting bolts (Fig. 3) or
(Fig. 4).
(6) Remove generator from vehicle.
Fig. 2 Generator B+ Cable and Field Wire
Connections (TypicalÐ4.0L Engine Shown)
1 - FIELD WIRE CONNECTOR
2 - B+ CABLE
3 - GENERATOR
4 - B+ CABLE MOUNTING NUT
5 - CABLE PROTECTOR
Fig. 3 Remove/Install GeneratorÐ4.7L V-8 Engine
1 - LOWER BOLTS
2 - REAR BOLT
3 - GENERATOR
WJCHARGING 8F - 27

INSTALLATION
INSTALLATION - 4.0L
SENSOR ONLY - 4.0L
The Camshaft Position Sensor (CMP) on the 4.0L
6±cylinder engine is bolted to the top of the oil pump
drive shaft assembly (Fig. 6). The sensor and drive
shaft assembly is located on the right side of the
engine near the oil filter (Fig. 7).
(1) Install sensor to oil pump drive.
(2) Install 2 sensor mounting bolts and tighten to
2 N´m (15 in. lbs.) torque.
(3) Connect electrical connector to CMP sensor.
OIL PUMP DRIVE AND SENSOR - 4.0L
(1) Clean oil pump drive mounting hole area of
engine block.
(2) Install new oil pump drive-to-engine block gas-
ket.
(3) Temporarily install a toothpick or similar tool
through access hole at side of oil pump drive housing.
Align toothpick into mating hole on pulse ring (Fig.
8).(4) Install oil pump drive into engine while align-
ing into slot on oil pump. Rotate oil pump drive back
to its original position and install hold-down clamp
and bolt. Finger tighten bolt. Do not do a final tight-
ening of bolt at this time.
(5) If engine crankshaft or camshaft has been
rotated, such as during engine tear-down, CMP sen-
sor relationship must be reestablished.
(a) Remove ignition coil rail assembly. Refer to
Ignition Coil Removal/Installation.
(b) Remove cylinder number 1 spark plug.
(c) Hold a finger over the open spark plug hole.
Rotate engine at vibration dampener bolt until
compression (pressure) is felt.
(d) Slowly continue to rotate engine. Do this
until timing index mark on vibration damper pul-
ley aligns with top dead center (TDC) mark (0
degree) on timing degree scale (Fig. 9). Always
rotate engine in direction of normal rotation. Do
not rotate engine backward to align timing marks.
(e) Install oil pump drive into engine while
aligning into slot on oil pump. If pump drive will
not drop down flush to engine block, the oil pump
slot is not aligned. Remove oil pump drive and
align slot in oil pump to shaft at bottom of drive.
Install into engine. Rotate oil pump drive back to
its original position and install hold-down clamp
and bolt. Finger tighten bolt. Do not do a final
tightening of bolt at this time.
(f) Remove toothpick from housing.
(6) Install sensor to oil pump drive. After installa-
tion, the CMP sensor should face rear of engine 0É.
(7) Install 2 sensor mounting bolts and tighten to
2 N´m (15 in. lbs.) torque.
(8) Connect electrical connector to CMP sensor.
(9) If removed, install spark plug and ignition coil
rail.
To verify correct rotational position of oil pump
drive, the DRB scan tool must be used.
WARNING: WHEN PERFORMING THE FOLLOWING
TEST, THE ENGINE WILL BE RUNNING. BE CARE-
FUL NOT TO STAND IN LINE WITH THE FAN
BLADES OR FAN BELT. DO NOT WEAR LOOSE
CLOTHING.
(10) Connect DRB scan tool to data link connector.
The data link connector is located in passenger com-
partment, below and to left of steering column.
(11) Gain access to SET SYNC screen on DRB.
(12) Follow directions on DRB screen and start
engine. Bring to operating temperature (engine must
be in ªclosed loopº mode).
(13) With engine running atidle speed, the words
IN RANGE should appear on screen along with 0É.
This indicates correct position of oil pump drive.
Fig. 10 CMP LocationÐ4.7L Engine
1 - RIGHT CYLINDER HEAD
2 - CAMSHAFT POSITION SENSOR
3 - MOUNTING BOLT
4 - ELEC. CONNECTOR
8I - 8 IGNITION CONTROLWJ
CAMSHAFT POSITION SENSOR (Continued)